FIELD TREATMENT OF TOBACCO EOOT-EOT. 7 



fertilizers were used. While none of the fertilized plots on the badly 

 diseased fields gave yields equal to those obtained from adjacent fields 

 free from disease, large differences in yield were obtained from the 

 fertilized plots. In all cases it was found that the plots on wliich 

 carbonate of potash was used gave the smallest plants and the lowest 

 yields. The use of lime with the carbonate of potash still further 

 diminished the yield. The use of carbonate of potash and lime with 

 cotton-seed meal and ground fish gave a yield of but 900 pounds per 

 acre. This yield was 200 pounds less to the acre than when no fer- 

 tilizer was used and was only a little more than half the yield obtained 

 from some of the other plots. These results indicate that the alkaline 

 condition of the soil resulting from the use of carbonate of potash and 

 lime favored the development of the root-rot. 



GREENHOUSE EXPERIMENTS WITH ALKALINE FERTILIZERS. 



The effect of alkaline fertilizers was tested further in a series of 

 greenhouse experiments made with a diseased soil from Connecti- 

 cut. All the pots were fertilized uniformly with cotton-seed meal. 

 To some of the pots one-half per cent of air-slaked lime was also 

 added. This cut down the weight of tobacco to nearly one-half 

 (53 per cent). Adding 2 per cent of lime decreased the weight to 

 35 per cent of that of the check plots. In soils free from root-rot, 

 the use of 1 per cent of lime gave a better growth of tobacco than 

 when no lime was used. This shows that the lime does not injure 

 the tobacco directly. The application of land plaster to the dis- 

 eased soil in amounts varying from one-half of 1 per cent to 2 per 

 cent had no bad effects and even slightly increased the growth of 

 tobacco. When lime was used with land plaster the weight again 

 decreased, averaging about 40 per cent of that of the checks. The 

 use of carbonate of potash in addition to the cotton-seed meal 

 decreased the weight of the tobacco to about 80 per cent of the 

 checks in spite of the fact that additional plant food was added. 

 The use of hydrochloric acid, on the other hand, increased the yield 

 by about 10 per cent, although this acid carries no plant food. 



The plants in the check pots in these experiments made a good 

 growth and were not seriously injured by the root-rot, although the 

 fungus could be seen on the roots. The root systems of the plants in 

 all the pots to which lime or carbonate of potash was added were 

 badly diseased. The roots of the plants grown in the soil in which 

 land plaster was used showed some disease, about like that of the check 

 pots. The roots of the plants grown in the acid-treated Soil were per- 

 fectly clean and white, and entirely free from the fungus. 



The soil used was originally from a badly diseased field. For a year 

 prior to these experiments it was used for growing tobacco in shallow 

 greenhouse beds provided with good drainage. This treatment 



[Circ. 7.] 



